The invention therefore lies in the technical field of extraction of biochemical or chemical analytes, especially DNA/RNA material, protein, cells and/or bacteria from samples, especially solid sample, such as soil samples, foodstuffs and the like, with subsequent reaction. For example, in the extraction of DNA/RNA from samples, the sample is combined with an extraction buffer in known fashion, mixed, and then filtered. The extract or filtrate is then usually subjected to further processing in a suitable container. This can be a molecular biology process (such as labeling during an immunoassay) or lysis during a DNA assay.
While the further processing of the extract on microfluidic scale is known—and this refers to filtrate amounts of less than 5 milliliters, typically on the order of 1 μl to 1000 μl and especially less than 500 μl—the extraction itself is carried out manually in several steps on a macroscopic or laboratory scale (filtrate amounts in the multiple-digit milliliter to liter range). A particular problem is the transfer of the extracted sample material to the microfluidic chip. In this way, a not inconsiderable loss of sample material can occur, as well as a risk of contamination for the transfer from one vessel to another. Moreover, it is not easy to introduce the extract into the chip without loss of fluidic control. Not least, extraction on a laboratory scale is costly and presupposes large quantities of the starting substances, especially the sample material.
A step in the direction of extraction is an extraction system as is described, for example, in the publication “Sample Preparation for the Analysis of Gluten from Foodstuff in a Modular Chip-Platform” on the occasion of the 10th International Conference on Miniaturized Chemistry and Life Science, from 5 to 9 Nov. 2006 in Tokyo, Japan. This extraction system uses a method based on a peristaltic or constricted tube pump for mixing the sample with an extraction buffer. To separate the undissolved sample components, a centrifuge is used instead of a filter. Efforts to reduce the centrifuging itself to the scale of microfluidic chips are described more closely in DE 10 2006 003 532 A1. The centrifuge is connected at the inlet and outlet side by a fluidic connection piece to a microfluidic chip.
Yet the technical expense of centrifuge extraction is very high. The centrifuge known from the aforementioned publication contains very many individual parts, some of them moving parts, and is therefore expensive, especially for a onetime use. Furthermore, the problems associated with the handling of the sample and the extract have not been solved. The filling of the extractor on the one hand and the transfer of the extracted sample material from the extractor to the centrifuge represent further problems. In this way, a not inconsiderable loss of sample material can occur, along with a risk of contamination during the transfer from one section of the apparatus to the next.
In summary, it can be said that the performance of the extraction due to the aforesaid reasons is at present cost-intensive, time-consuming, and involves a heightened risk of contamination for personnel and surroundings.
The extraction and preparation of a sample in chip format, i.e., in microfluidic amounts, by means of a module which can be directly connected to a microfluidic chip or a microfluidic arrangement is not known at present.
From WO 2006/029387 A1 is known a portable extraction device with a syringe-like arrangement for pipetting and dispensing an analyte, preferably a nucleic acid, to a purification chip. Between the syringe arrangement and the purification chip, a valve to guide the fluid flow and a filter arrangement are hooked up.
From DE 44 32 654 A1 is known a filtration arrangement for preparation of nucleic acids from natural sources with a syringe-like arrangement, by which the disintegration from the nucleic acid is furthered by a filtration arrangement located upstream from the outlet of the syringe arrangement.
A mere miniaturization of known filtration methods, however, would involve further problems. Traditional filter arrangements for sample extraction have the drawback that the filter pores very quickly get clogged, which necessarily places a limit on miniaturization. A large pressure difference during the filtration would moreover lead to a very fast transport of the extract in a connected microfluidic chip, which would jeopardize the fluidic control there. Also, the pressure strength of the usual microfluidic chips would not be able to withstand the pressures occurring during filtration.
The goal of the invention is to overcome the above problems.